1. Field of the Invention
The present invention is directed to a gas discharge lamp such as a flashbulb in which the cathode is a sintered powdered metal composite containing titanium, vanadium, and Ta and/or Nb.
2. Description of the Prior Art
Gas discharge lamps normally contain two electrodes in a gas-filled, light-permeable housing. The cathode is normally connected to a lead which is conducted through the housing in vacuum-tight fashion and the cathode is connected thereto.
It is also known to form the cathode as a porous sintered member. Salts of alkaline or alkaline earth metals are embedded into the pores of the sintered member. Any such sintered member should have a combination of characteristics to a greater or lesser degree. First, the porosity should be optimally high in order to provide the embedded salts with a large surface. The solidity should be high and, in particular, no particles should separate from the cathode during operation of the lamp. The ductility and shearing strength should be very high because the cathodes are usually secured to the power lead by mechanical affixation such as stamping or pressing during mass production, and are thereby greatly deformed. Next, the metals used should have a high melting point. Lastly, the metals used should have a high affinity for oxygen, hydrogen, carbon monoxide, and carbon dioxide, i.e., they should act as getters.
As will be appreciated, no single composition meets these requirements completely and a compromise has to be effected by choosing from a plurality of metal powders in making up the compact.
In JP-A-58/106761, there is disclosed a sintered cathode for flashbulbs composed of Ta, Nb, or alloys of the two.
In DE-A-33 29 270, there is a disclosure of a flashbulb wherein the cathode is a sintered member composed of the metals W, Mo, Ti, Ni, Ta and Nb.
In DE-A-29 35 447, there is described a sintered electrode for flashbulbs composed of a basic metal (W,Mo,Ta or a mixture of these metals) and of an alkali earth metal or earth metal compound. A metal oxide of yttrium, zirconium, aluminum, or mixtures thereof is also present in the sintered member.